Film processor drying control



Feb. 26, 1952 J. w. GILLoN FILM PROCESSOR DRYING CONTROL Filed Jan. 4, 19,51

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Patented Feb. 26, 1952 UNITED STATES John W; Gillon, Hartsdale, N. Y., assigner to Generalv Precision Laboratoryv Incorporated,y a corporation of New York ApplicationV January 4, 1951, Serial No. 204,361

8 Claims.

This invention pertains to controls for photographic lm developing processors, and more specifically to controls for the drying operation in motion picture nlm processing.

It is especially necessary to control the lmdrying process accurately in rapid film developing processes such as are used in recording television programs for either immediate and/or subsequent projection. In such processes the entire processing of the film including developing, fixing,washing and drying is accomplished in a minuteor less, with only fifteen seconds of this time allotted for drying the lm. At the same timethe lm must be effectivelydried so that it may be used immediately for projection.

The mechanism of a rapid processor in general consists of a light-tight cabinet having in succession separate chambers for develop-ing, rinsing, fixing, Washing and drying the exposed film. The iilm is fed from a supply reel or directly from the camera and is threaded over a series of rollers which continuously pass the film through the successive developing, rinsing, fixing, Washing and drying chambers. From the drying chamber other rollers pass the lm either to storage reels or directly to a projector. When the film is ed directly iromfa camera to the rapid processor and directly therefrom to a projector the rate rof travel through the processor must necessarily be that of travelv through the kcamera and projector, which is 24 frames per second for sound' nlm, and in the case of `16 mm. nlm is k9.6 feet per second.

`It is very desirable to keep the time of lm travel through the processor as short as possible, i and to keep the physical 'dimensions of the i .processor small. VTo do so when the film travel `rate is so high requires that the efficiency of the nlm-drying component of the processor be high. In the present invention infra-red drying is employed with the vapor-laden air removed bysuction.

The speed of dryingof anyparticular section of a developed motion picture iilm strip depends upon the amount and length of time the infrared energy is directed upon it, the speed of air scavenging and nally upon the nlm opacity or transparency. Dense nlm intercepts a `greater proportion of the infra-red energy radiated toward it, converting it into sensible heat which in turn raises the temperature of the iilm and the vapor pressure of the moisturecontained in the gelatine thereon and supplies the latent heat for vaporization thereof. Completely transparent nlm, on .the other hand, -intercepts only a small 2 amount of radiant `energy impinging` upon it, so that the drying effect produced thereon is much less than the drying effect produced by the same amount of infra-red energyy impinging on completelyfexposed lm which has-the maximum possible opacity.

In designing la rap-id process drying compartment it is not possible to apply enough heat to dry transparent nlm in the time allotted without overheating dense film, resulting in the gelatine i being crinkled or even in being completely melted `from the denser parts `of the film. On the other hand, if only sufiicient radiant heat is applied 'to the film to dry the dense portions the transparent portions Will not be thoroughly dried 4and vwhen reeled the still damp lm may stick and dropletsof Water remaining thereon may `cause spotting.

in orderr to overcome this problem the instant invention monitors thedeveloped nlm before it enters kthe drying compartment to ascertain its density or-.transparency and adjusts the applied quantity of infra-red radiation accordingly. The monitoring Ioperation is accomplished by means of a light-sensitive device placed on one side of the moving film and asmall light source placed on the otherside thereof, so' that the output of `the light-sensitive device is a measure of lm transparency. The source of infra-red radiation consists of two sets of incandescent heat lamps,

`a regular group and an auxiliary group. The regular group has an intensity sufficient to dry nlm whose density is above a selected amount, and the auxiliary group of lamps when combined withthe regular set provides an increased aggregate intensity sufficient to dry transparent film. Theregular group is operated continuously and the auxiliary group is turned on by a signal derived from the light-sensitive source when the iilm density'is vbelow the above mentioned selected amount.

Since any film section takes about l5 seconds to pass through the drying compartment, any transparent portiomeven if short, should be exposed to the necessary increased heat radiation for such length of time as to insure its being thoroughly dried. This requires the addition of `a time delay element so that, after the auxiliary group of `lamps has been turned on, it will remain on for the desired time, which may be the time required for the transparent element to complete its passage through the dryer or may be less, after which theauxiliary group of lamps will beturned ofi. If, however, during the passage 1of the transparent element through the 3 dryer, another transparent element should enter the monitoring section, the auxiliary group control equipment is automatically reset so that the additional lamps are not turned off until the later transparent element has passed through the dryer.

In order to prevent the accumulation of heat energy in the drying compartment with a consequent destructive temperature increase, all surfaces therein are made highly specular and as non-absorptive as possible. In addition a safety cutoff may be provided.

The general object then of this invention is to provide motion picture nlm drying equipment which discriminates between nlm sections the density of which is greater or less than a preselected value.

More specifically, the object of this invention is, in a film processing machine, to control the application of radiant drying heat to the nlm in accordance with its relative transparency.

Another object of the invention is, in a mo tion picture nlm rapid processing machine, to increase the quantity of infra-red energy applied to the nlm when the nlm is more transparent to such energy than a preselected amount, and to decrease the quantity of infra-red energy applied when the nlm is less transparent than such preselected amount.

A further understanding of this invention may be secured from the detailed description together with the accompanying` single drawing ngure in which the mechanical arrangement and the electrical circuit are schematically depicted.

Referring now to the single ngure, a rapid nlm processor is provided with a drying compartment Il for drying a motion picture nlm strip I2 delivered to it from a preceding washing compartment. The nlm strip is passed from an entrance tunnel I3 through a monitoring cell I4, i

to be described later, thence through a narrow exit slit I5 and tube I5 acting as a light exclusion trap, into the drying chamber II, where the nlm is passed over a series of upper rollers I6 and lower rollers I1 having a capacity of say nine feet of nlm. In leaving the last roller I8, the nlm is withdrawn from the compartment through a slit I9 to ybe either wound on a storage reel or fed directly to a projector.

During the interval in which the nlm strip is encompassed in the drying chamber it is irradiated by heat rays derived from one or more infrared lamps, six of which, 2|, 22, 23, 24, 25 and 26 are shown in the ngure. These lamps are divided into two groups. The first or regular group may consist of any desired number of lamps, it being required only that the intensity of radiation from this group shall be adequate to dry nlm of average density or opacity. In the figure this group is represented by a single lamp 2| which is continuously energized from a standard power source through the medium of conductors -21 and 28. The second or auxiliary group consists of lamps 22 to 26 having an aggregate power that in general will be several times that supplied by the regular group, their power being sufficient in combination with the power of the regular group to dry completely transparent nlm during all or a selected fraction of the travel of such a nlm section through the chamber. These auxiliary lamps are connected in parallel with each other and to a 11E-volt power source in series with suitable control equipment, so that they are energized only during the time that a transparent or 4 low density section of nlm is traveling through the chamber.

The control equipment consists nrst of a monitoring source of light 29 contained in the monitoring cell I4. The light 29 may conveniently be an ordinary small neon lamp or a stroboscopic neon lamp operated from the usual power mains. The lamp 29 is placed on one side of the nlm strip 3| so that the light emitted thereby falls on the nlm strip I2 as it is drawn through the monitoring cell. The degree of transmission by any portion of the exposed nlm strip of the variations emitted by the neon lamp is approximately the same as the degree of transmission by the same portion of nlm strip as respects infra-red radiation, so that the amount of neon light illumination passed by a portion of nlm in the monitoring cell I4 is a measure of the amount of infra-red which will be transmitted by the same portion later as it passes through the drying chamber, and such transmission characteristic is an inverse function of the amount of radiation absorbed and hence its drying effect. Since the neon lamp is energized from a 60-cycle source, the resulting light produced thereby is modulated at a C. P. S. rate. The fraction of this modulated light which is passed through the nlm 3| is directed onto the cathode 32 of a gas phototube 33, the anode 34 of which is energized from a well-iiltered direct-current source represented by terminal 36 having an additional nlter represented by resistor 31 and condenser 38. A load resistor 39 is connected in series with the phototube anode 34 and its source 36, a small condenser 4I, of say, 500 M. M. F. capacity, being connected to the anode terminal 42 to nlter out any high frequency components which may be present. The 1Z0-cycle modulation component of the light produces a variation of the internal impedance of the phototube at the same fre quency having an amplitude proportional to the degree of light transmission of the nlm 3|. This impedance variation produces a corresponding variation of current in the load resistor 39 and of voltage at the terminal 42.

The 1Z0-cycle voltage variation existing at terminal 42 is applied through a condenser 43 to the control grid 44 of an ampliner tube 46, to produce an amplined alternating voltage at the anode terminal 41. The tube 42 may be followed by any desired number of ampliner stages, but for purposes of illustration the tube 42 is shown as coupled through conventional condenser coupling to the nnal ampliner stage comprising a thyratron 48. The tube 48 has its anode energized by a 60-cycle alternating current supply so that the current therethrough falls to zero every cycle. The grid bias therefor is supplied in the usual way so that a very small plate current nows in the absence of an input signal. The input signal is applied to the control grid 49 in such phase relation as to produce an anode current of a magnitude representative of the input signal intensity. The cathode 5| is grounded through a relay coil 52 shunted by a condenser 53, resulting in an average direct current iiow inJ0 the coil representative of input signal intens1 y.

Associated with the relay coil 52 are contacts 54 having a pick-up value representing a dennite input signal intensity, which in turn represents the degree of nlm heat transmission at which it is desired to energize the auxiliary group of infrared lamps. The contacts 54 when closed energize ausm-as i the coil 55 of a time delay. relay. 5B having instantaneous pick up and delayed release. The

'relay 56 is of the plunger type having an iron armature 51 connected by a brass rod 58 with a contact crossl piece 759. .When the coil 55 is energized the armature 5i' is pulled up, the cross piece 59 closes the circuit between two fixed-contacts 6 l and 62, and the internal follow` spring 63 is compressed until the armature 51 is vprevented from further movement by a stop 64. armature 51 travels upward it draws with it a piston 66 to which it is connected by a rod 61, the piston 55 working in a dashpot 68 filled with oil. The piston 65 is designed to move upward unimpeded by the oil but moves downward under the combined weight of the armature and the pressure of spring 63 only as fast as the oil is permitted to ow through an adjustable orice 69, the expanded piston leather 1I preventing leakage between it and the cylinder wall. As the piston falls, the cross piece 59 breaks contact with the fixed contacts 5l and 62, the time of fall to break being adjustable between one and Iifteen seconds by means of the adjustable orifice 69.

When the contacts 6l, 52 are connected by the contact cross piece 59, a circuit is closed which includes the power supply conductors 12, 12 and a load consisting of the auxiliary lamp group composed of lamps 22, 23, 24, 25 and 26. These lamps are therefore energized as soon as the relay 55 is closed and remain energized until the end of the opening time delay period. If, during the relay time delay period the relay should again be energized, as by a second section of highly transparent nlm passing between the lamp 29 and cell 33 the armature 51 is again drawn upward and the full time delay period is reinitiated.

If a short length of say, one foot of nearly transparent lm should be succeeded after almost nine feet of opaque film and then by another short length of nearly transparent film, the auxiliary lamp bank would be kept burning continuously. Under such circumstances the incidental heat storage in the walls and air of the drying chamber are liable to cause such a rise of temperature in opaque portions of film as to endanger them. In order to provide against such a contingency a bimetallic thermostat 13 is provided having one-side of its bimetal strip blackened so as to be exposed to the same degree of temperature rise under infra-red radiation at any selected degree of ambient temperature as opaque or Very dense film strip. The thermostat 13 is positioned for exposure to the auxiliary lamp radiation, and its contacts 14 are connected in l series with the auxiliary lamp circuit, so that a sustained degree of infra-red irradiation which would be liable to endanger the lm results in the opening of the auxiliary lamp circuit. At the same time, the thermostat automatically restores the circuit when it and the film have cooled to a safe temperature.

What is claimed is:

1. In a motion picture lm processor, an apparatus for drying a moist developed motion picture strip comprising, a drying chamber, means contained therein for supporting said motion picture strip as it is passed therethrough, a source of continuously energized heat radiation in said drying chamber positioned to direct heat rays on said lm strip, means associated with said lm strip for ascertaining the density thereof, an auxiliary source of heat radiation in said drying chamber, a circuit for energizing said auxil- .iaryasourca t' switch `meansin said. circuit Iconf trolledy by said means for-ascertaining ,the density offsaid liilm strip, and` means associated with, said switch means for maintainingsaid switch means closed for a predetermined timeafter actuation thereof.

2.A-pparatus aas: dei-ined in claim 1 in which said means` for ascertainingthe densityof` said ilxn strip comprises a light source and a phototube positionedon opposite sides of said film strip.

3. In a motion picture film processor, an apparatus for drying a moist developed motion picture strip comprising, a drying chamber, means contained therein for supporting said motion picture strip as it is passed therethrough, a normally energized infra-red source positioned to project infra-red rays developed thereby on said lm strip, means located adjacent the point of entry of said nlm strip into said drying chamber for ascertaining the average density of said lm strip, an auxiliary infra-red source positioned in said drying chamber, a circuit for energizing said auxiliary source, switch means in said circuit controlled by said means for ascertaining the density of said lm strip and means associated with said switch means for abruptly closing and delaying the opening thereof.

4. Apparatus as defined in claim 3 in which said means for ascertaining the average density of said lm strip comprises a light source and a phototube positioned on opposite sides of said film strip.

5. In a motion picture lm processor, an apparatus for drying a moist developed motion picture strip comprising, a drying chamber, means contained therein for supporting a predetermined length of said motion picture strip as it is passed therethrough, a source of continuously energized heat radiation in said drying chamber positioned to direct heat rays on said iilm strip, means associated with said film strip for ascertaining the density thereof, an auxiliary source of heat radiation in said drying chamber, a circuit for energizing said auxiliary source, switch means in said circuit controlled by said means for ascertaining the density of said lm strip, means associated with said switch means for maintaining said switch means closed for a predetermined time after actuation thereof, and additional circuit interrupting means connected in said circuit and located in said drying chamber for interrupting said circuit when the ambient temperature of said chamber exceeds a predetermined limit.

6. Apparatus as defined in claim 5 in which said means for ascertaining the density of said lm strip comprises a light source and a phototube located on opposite sides of said lm strip.

1. In a motion picture lm processor, an apparatus for drying a moist developed motion picture strip comprising a drying chamber, means contained therein for supporting said motion picture strip as it is passed therethrough, a normally energized infra-red source positioned to project infra-red rays developed thereby on said film strip, means located adjacent the point of entry of said film strip into said drying chamber for ascertaining the density of said lm strip, an auxiliary infra-red source positioned in said drying chamber, a circuit for energizing said auxiliary source, switch means in said circuit controlled by said means for ascertaining the density of said lm strip, means associated with said switch means for abruptly closing and delaying the opening thereof, and additional circuit interrupting means connected in said circuit and 1ocated in said drying chamber for interrupting said circuit when the ambient temperature of said chamber exceeds a predetermined limit.

8. Apparatus as defined in claim 7 in which said means for ascertaining the density of said film strip comprises a light source and a phototube located on opposite sides of said lm strip.

JOHN W. GILLON.

REFERENCES CITED The following references are of record in the file of this patent:

5 UNITED STATES PATENTS Number Name Date 2,278,767 Brophy Apr. 7, 1942 2,355,391 Nelson et al Aug. 8, 1944 m 2,413,218 Coroniti Dec. 24, 1946 

